ClanLib

ClanLib is a cross-platform game SDK currently
supporting Windows and Linux. It provides
easy-to-use interfaces for 2D graphics, input,
sound, resources, networking, GUI, OpenGL, and
more. The goal is to provide a game SDK that does
all the dirty work that all modern games need to
implement anyway, thus making the game developer
concentrate on the gameplay instead of reinventing
the wheel over and over again.